The present invention relates to a hydraulic torque transmitting apparatus and more particularly to a hydraulic torque converter which is mounted on an automatic transmission for automotive vehicles or the like.
A hydraulic torque converter in which power from an engine is once converted into kinetic energy of a fluid and the energy is then taken out as torque is disclosed for example in U.S. Pat. No. 3,165,946 as shown in FIG. 1.
Such a hydraulic torque converter generally forms an automatic transmission with a planetary gear set and a gear shift control device and is adapted to smoothly transmit power from an engine to a propeller shaft and the like via the planetary gear set.
A crank shaft, that is, and input shaft (not shown) of an engine is connected with a drive plate boss 1a of an impeller 1. The other output shaft (not shown) is connected with a boss 2a which is integral with a turbine rotor 2. The impeller 1 and the rotor 2 are disposed so that they oppose each other with a given clearance .delta..sub.1 (for example 3 mm) at the outer periphery thereof.
In other words, a shell 3 of the impeller 1 which is in the form of a half torus is provided with a plurality of (for example 24) radially extending vanes 4 projecting from the inner periphery 3a thereof within the inner space thereof. The vanes (or blades) 4 are retained between the shell 3 and a half torus-shaped core ring 5 which is disposed within the shell 3. Another half torus-shaped shell 8 of the rotor 8 which opposes to the shell 3 is similarly provided with a plurality of radially extending vanes 7 projecting from the inner periphery 8a' thereof within the inner space thereof. These vanes 7 are retained between the shell 8 and a half torus-shaped core ring 9.
A stator 11 having radially extending vanes 10 is disposed on and around a one-way clutch which is positioned on the output shaft (not shown) axially between the impeller 1 and the rotor 2 and at the radially central space.
When the input shaft is rotated in synchronization with the engine, the impeller 1 directly fixed to the input shaft is also rotated integral with the input shaft. Oil within the shell 3 is also rotated by being propelled by the vanes 4 so that the oil is forced to move in a radially outer direction by generated centrifugal force. Oil in the central space of the shell 3 is also successively forced to move to the radially cuter periphery. Accordingly the oil which has been moved to the radial outer periphery of the shell is expelled into the inside of the shell 8 of the rotor 2 after passing through the clearance .delta..sub.1. At this instant, the influent oil into the rotor 2 impinges upon the vanes 7 so that the resulting impact force causes the rotor 2 to rotate in the same direction as that of the impeller 1. The oil which has impinged upon the vanes 7 flows along the vanes radially inward and toward the stator 11. Oil coming out of the stator 11 flows again within the shell 3 of the impeller in the radially outward direction. The reaction force of the influent oil further increases the rotation torque of the impeller 1.
In the hydraulic torque converter, the kinetic energy of the oil from the rotor 2 is effectively utilized by the impeller by rectifying the flow direction of the oil by the vanes 10 of the stator 11 so that the more the difference between the rotational speeds of the impeller 1 and the rotor 2 becomes, the more the rotation torque of the rotor 2 increases.
Upon assembly of the hydraulic torque converter, the vanes 4 (or 7) are secured and sandwiched by and between the shell 3 (or 8) and the inside core ring 5 (or 9), respectively. Thereafter the outer peripheral end 8a of the shell 8 and the outer peripheral end 5a (or 9a) of the core ring 5 (or 9) are machined so that the outer peripheral ends 5a and 9a of the core rings 5 and 9 will not contact or interfere each other on rotation, and a given clearance .delta..sub.1 is assured between the ends (4a and 7a) of the vanes 4 and 7.
However when the outer peripheral ends 5a and 9a of the core rings are machined, the corners of the vane ends 4a and 7a are readily damaged by for example the contact with a cutting tool. In order to positively avoid such damages, it should be designed so that the opposite vane ends 4a and 7a are preliminarily sufficiently set back from the outer peripheral end 8a of the shell 8 or the outer peripheral ends 5a and 9a of the core ring. Accordingly the clearance .delta..sub.1 between the impeller 1 and the rotor 2 becomes wider (.delta..sub.1 &gt;.delta..sub.2 in the drawing) so that a problem rises that the rotor efficiency is remarkably decreased due to the leakage of the oil through the clearance .delta..sub.1.